Hydraulic anchor



Jan. 16, 1968 H. L. MOGILL 3,363,695

HYDRAULIC ANCHOR Filed Nov. 8, 1965 2 Sheets-Sheet l Howard Z. We 6///INVENTOR.

ATTO/P/V Filed Nov.

H. 1.. M GILL 3,363,695

HYDRAULIC ANCHOR 2 Sheets-Sheet 2 J m L 57 43 Howard 1. Mr

INVENTOR. 45

United States Patent 3,363,695 HYDRAULIC ANCHOR Howard L. McGill,Houston, Tex., assignor to Schlumberger Well Surveying Corporation,Houston, Tex, a corporation of Texas Filed Nov. 8, 1965, Ser. No.506,664 13 Claims. (Cl. 166120) ABSTRACT OF THE DISCLOSURE As oneembodiment of the invention disclosed herein, a pressure-responsiveanchor is coupled to a well packer that is adapted for actuation bymovement of a tubing string. Selectively-operable valve means arearranged for actuation by movement of the tubing string so that untilthe packer is set, the anchor is isolated from actuating fluidpressures. Once the packer is set, however, the valve means are openedto admit fluid pressures in the tubing string to the anchor.

Accordingly, as will subsequently become apparent, this inventionrelates to apparatus adapted for anchoring a well tool in place withinthe well bore; and, more particularly, to hydraulically actuated anchorswhich are normally disabled and selectively actuatable to be securedagainst hydraulic pressures in the well by an anchoring forceproportionately related to the acting pressure.

In conducting such well-completion operations as acidizing, cementing,or fracturing, a full-opening Well packer dependently coupled from atubing string is positioned at a particular depth in a cased well andthe packer set to isolate the formation interval to be treated from theremainder of the Well bore thereabove. Treating fluids are then pumpeddownwardly at high pressure through the tubing and full-bore packer andintroduced into the formation being treated through perforationsappropriately located in the casing.

It will be appreciated that after the packer is set, whatever fluidsthere may be in the tubing string ahead of the treating fluid will bedisplaced therefrom by the treating fluids. With the packer set, thesefluids must, of course, be forced into the formation ahead of thetreating fluids. Accordingly, in a typical cementing operation, forexample, it is customary to fill as much as practical of the tubingstring with cement before the packer is set to minimize the volume ofunwanted fluids that would otherwise be displaced into the formation. Toaccomplish this, the tubing string is filled to within a few hundreds offeet above the retracted packer and pressure is applied to the wellannulus to maintain the cement up within the tubing. Then, by carefulcoordination, the packer is set at a predetermined depth as the pressurein the annulus above the packer is reduced and pressure applied to thetubing string to force the cement downwardly at high pressure. Bycarefully controlling the sequence of these operations, the cement ishopefully discharged from the lower end of the tubing below the packeralmost immediately after the packer has been firmly set. In this manner,the volume of unwanted fluids in the tubing string that must bedisplaced into the formation ahead of the cement is held to a minimum.

Once the packer is set, it will be recognized that it will be subjectedto a high, upwardly directed pressure ditlerential from the cement andmust, therefore, be securely anchored against upward movement.Heretofore, it has been customary to employ movable anchoring memberswhich are hydraulically extended against the casing by the fluid passingthrough the tubing to secure the packer against such upward movement.

Typical of such anchors is the one described in Patent No. 2,792,063.Although anchors such as this are being successfully employed in thesecompletion operations, it is recognized that they can be prematurelyactuated before the packer has been fully set. For example, in acementing operation as just described, as the column of cement is firstpumped downwardly, its greater density can cause the anchoring elementsto extend before the packer has been firmly set. Although such anchoringelements are typically arranged to prevent only upward movement of thetubing string, they can, however, engage the casing wall with such forcethat further downward travel of the string will be either retarded ortotally halted. Should this occur, it is quite possible that suflicientdownward travel of the tubing string will not be obtained to fully setthe packer. Obviously, unless the packer is fully set, it will beincapable of providing a fluid-tight seal; and is very likely thatcement will flow up around the packer element and result in aninadequate cementing job.

Accordingly, it is an object of the present invention to provide new andimproved anchoring apparatus for well packers, which apparatus hashydraulically actuated wall-engaging members that are normally disabledand selectively releasable only after the packer is firmly set foranchoring engagement with a well bore with a force proportionatelyrelated to the pressure of fluids in the tubing.

This and other objects of the present invention are attained byproviding a well packer that is operated in response to a force throughthe tubing string for packing off a Well bore with anchoring means thatare responsive to fluid pressure to secure the packer to the wall of thewell bore and means for selectively applying such fluid pressure to theanchoring means in response to a greater force on the tubing string tosecure the packer only after the well bore has been packed-off.

The novel features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of a certain embodiment when taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a view of a full-bore packer having an anchor thereonemploying principles of the present invention and depicted as they wouldappear within a well bore;

FIG. 2 is a detailed cross-sectional view in elevation of the anchordepicted in FIG. 1 in its retracted position;

FIG. 3 is a cross-sectional view taken along the lines 3-3 of FIG. 2;and

FIG. 4 is a view similar to FIG. 2, but showing the anchor as it willappear when anchoringly engaged.

As seen in FIG. 1, a typical so-called compressionset full-bore packer10 is dependently connected in a tubing string 11 and positioned withina well bore 12 having a casing 13 set therein and secured by a column ofcement 14. A hold-down or anchor 15 incorporating the principles of thepresent invention is serially coupled between the upper end of thetubular mandrel 16 of the full-bore packer 10 and the lower end of atypical valve 17, which is, in turn, connected to the lower end of thetubing spring 11. As is conventional in the art, the bypass valve 17 isopened to divert some of the fluids therein through the central bore 18of the packer mandrel 16 whenever the full-bore packer 10 is beingshifted 3 within a fluid-filled well. After the packer has been set, thebypass valve 17 is, of course, closed to prevent fluid communicationbetween the tubing string 11 and the well annulus above the sealinglyengaged packer.

The typical full-bore packer 10 shown in FIG. 1 includes a tubularhousing 19 through which the mandrel 16 is slidably disposed. Anelastomeric packing element 20 is mounted above the housing shoulder 21and a slidably disposed slip bowl 22 on the mandrel 16. Normallyretracted slip members 23 are operatively mounted around the housing 19and cooperatively engaged with the slip bowl 22 in the well-knownmanner. Conventional drag blocks 24 are arranged to secure the housing19 to the casing 13 as the mandrel 16 is manipulated relative to thehousing to extend the packing means 20 and slips 23 against the casing.A system of conventionally arranged so-callcd Jslots and J-pins (notshown) selectively latch the mandrel 16 relative to the housing 19 tokeep the packer 10 retracted.

Accordingly, when the packer 10 is to be set, the tubing string 11 ispicked up slightly and then manipulated as required by the arrangementof ]-slots to free the mandrel 16 for downward travel. As the mandrel 16is lowered, the drag blocks 24 restrain the housing 19 against downwardmovement as the mandrel successively drives the slip bowl 22 downwardlyto extend the slips 23 and foreshortens the packing means 20. By thetime the mandrel 16 has reached its lower limit of travel, the slips 23will be engaged against the casing 13 and the packing means 20 displacedinto sealing engagement therewith. To ensure that the packing means 20are fully displaced, at least part of the weight of the tubing string 11is slackedoff to impose a substantial downward force through the packermandrel 16 and shoulder 21 to the packing element. It will beappreciated of course that, once set, the slips 23 will prevent thepacker 16 from. being moved further downwardly within the casing 13 bysuch downward forces. It should also be noted that the bypass valve 17is typically arranged to be closed as the packer 10' is being set. Thus,once the packer 10 is set, the bypass valve 17 will also be closed andblock fluid communication from below the packer and the annulus abovethe packer.

As will be subsequently explained, a self-contained hydraulic systemwithin the anchor is arranged to operatively actuate the anchor inresponse to a pressure below the packing means that is greater than thatabove. Thus, whenever the bypass valve 17 is closed and the packingmeans 20 set, an increased pressure below the packer 10 will beelfective to anchoringly engage the anchor 15 with the casing 13 tosecure the packer mandrel 16 against upward shifting.

Turning now to FIG. 2, the anchor 15 is comprised of a tubular mandrel25 having anchoring means 26 around the upper portion and its lowerportion telescopically received within and extending substantiallythrough a tubular housing 27 to define an annular space 28 between thetwo members. Coupling means, such as threads 29 and 30, are provided atthe upper and lower ends of the mandrel 25 and housing 27, respectively,for coupling the anchor 15 into a string of tools as shown in FIG. 1. Alongitudinal bore 31 of uniform diameter extends through the mandrel 25.

A central portion 32 of the mandrel 25 is enlarged and fluidly sealedwithin the upper end of the housing 27 by an O-ring 33. To limit thedownward travel of the mandrel 25 relative to the housing 27, shoulder34 is provided by the upper end of the housing and normally spaced belowan external mandrel shoulder 35. Complementary splines and grooves, asat 36, on the mandrel 25 and in an internal housing shoulder 37co-rotatively secure the members to one another. An external mandrelshoulder 38 spaced below the splines and grooves 36 is adapted to engagethe lower face of housing shoulder 37 to limit the upward travel of themandrel 25.

The mandrel 25 is normally supported in an elevated position (as seen inFIG. 2) relative to the housing 27 by an exceptionally heavy compressionspring 39 confined within the annular space 28 and engaged between thelower face of the mandrel shoulder 38 and a retaining ring 41) restingon an internal housing shoulder 41 therebelow. A second and much weakercompression spring 42 is also arranged within the annular space 28 andengaged between the retaining ring 46 and the upper face of an annularfloating piston member 43 that is fluidly sealed to the mandrel 25 andhousing 27 by O-rings 44 and 4 5.

The anchoring means 15 mounted around the upper portion of the mandrel25 are comprised of an expansible elastomeric sleeve 46 encircling themandrel and a plurality of elongated wall-engaging members 47 and 48mounted longitudinally and spaced uniformly around the periphery of thesleeve. The enlarged upper and lower ends 49 and 5% of the elastomericsleeve 46 are secured by slidable annular retainers 51 and 52 withinopposed peripheral recesses 53 and 54 around the mandrel 25. 0- rings 55and 56 fluidly seal the sleeve ends 49 and 51) within the recesses 53and 54 to provide a fluid-tight space 57 between the sleeve 46 andmandrel 25.

Each of the casing-engaging members 47 and 48 is elongated and has athick, arcuate cross-section (FIG. 3). Alternate ones 47 of thecasing-engaging members are centrally aligned and mounted on the outerconvex surface of relatively thin, elongated, arcuate backing members58. A suflicient number of these mounted members 47 are disposeduniformly around the periphery of the elastomeric sleeve 46 that thebacking members 58 substantially encompass the sleeve. The remainingcasingengaging members 48 are unmounted and alternately disposed betweenthe mounted casing-engaging members 47 in such a manner that theunmounted members 48 straddle adjacent backing members 58 and cover thegaps 59 therebetween.

The ends of the casingengaging members 47 and 43 are beveled, as 60(FIG. 2), for reception within the opposed annular mandrel recesses 53and 54. Springs 61 and 62 are operatively engaged at opposite ends ofeach of the members 47 and 48 to bias the members inwardly. It will beappreciated, therefore, that although the casingengaging members 47 and4 8 will be moved radially outwardly against the springs 61 and 62whenever the elastomeric sleeve 46 is inflated, the beveled ends of themembers cannot escape from the mandrel recesses 53 and 54.

Turning now to the hydraulic actuating means of the anchor 15. Thefluid-tight space 57 between the elastomeric sleeve 46 and mandrel 25 isconnected, by way of a longitudinal passage 63 through the enlargedmandrel portion 32, to the upper end of the annular space 64 below theO-ring 33 and above the upper housing shoulder 37. Although there isfluid communication through the clearance between the splines andgrooves 36, an O-ring 65 around the lower portion of the upper housingshoulder 37 fluidly seals the housing 27 relative to the mandrel 25 atthis point to prevent fluid communication into the annular space 28therebelow.

Thus, it will be appreciated that so long as the mandrel 25 is elevatedwith respect to the housing 27 as illustrated in FIG. 2-, the O-ring 65prevents fluid communication between the two annular spaces 64 and 28respectively above and below the O-ring 65. The hydraulic system is,therefore, divided into upper 66 and lower 67 portions. The upperfluid-tight portion 65 is comprised of the fluidtight space 57 inside ofthe elastomeric sleeve 46, the longitudinal passage 63 and the upperannular space 64 between O-rings 33 and 65; and the lower hydraulicportion 67 is comprised of the intermediate portion of the annular space28 below the O-ring 65 and above the annular piston member 43. Toprovide means for selectively controlling communication between the twoabove-described portions 66 and 67 of the hydraulic system, the mandrel25 is slightly reduced in diameter, as at 68, im-

mediately above where it is sealingly engaged with O-ring 65 wheneverthe mandrel is elevated.

Accordingly, whenever the fiuid-tight hydraulic portions 66 and 67 arefilled with a suitable hydraulic tluid through conveniently locatedfilling ports (not shown), it will be understood that there is no fluidcommunication therebetween so long as the mandrel 25 remains in itselevated position (FIG. 2) relative to the housing 27. When, however,the mandrel 25 is shifted downwardly relative to the housing 27,communication will be established between the two fluid-tilled portions66 and 67 whenever the reduced mandrel portion 68 is shifted below theO-ring 65 a suflicient distance to permit hydraulic fluid to passbetween the O-ring 65 and mandrel.

Thus, by shifting the mandrel 25 downwardly relative to the housing 27,it will be understood that whatever pressure is acting within thelowermost portion of the annular space 28 below the piston 43 will urgethe piston upwardly to develop a corresponding hydraulic pressurethroughout both of the hydraulic system portions 66 and 67 and, mostparticularly, in the fluid-tight space 57 under the elastomeric sleeve46. The pressure below the annular piston 43 is, of course, the same asthat within the tubing string 11 in view of the clearance 69 at thelower end of the mandrel 25 and housing 27. Moreover, it will beappreciated that whenever the packer is set, the pressure in the tubingstring 11 and below the packer will be actmg upwardly on the piston 43and the hydrostatic pressure above the packer will be acting inwardly onthe elastomeric sleeve 46.

Turning now to the operational relationship of the anchor 15 and thefull-bore packer 10. When the string of tools shown in FIG. 1 are beingpositioned in a well bore, the heavy spring 39 will hold the mandrelelevated relative to the housing 27 and the full-bore packer 10. It willbe appreciated therefore, that before the packer 10 has been set, theupper portion 66 of the hydraulic system will be closed-oil from thelower portion 67 by the sealing engagement of O-ring 65 with the mandrel25. The hydraulic pressure in each of the portions 66 and 67 of thehydraulic system will, however, be substantially equal to thehydrostatic pressure of the fluids in the well since both the expansiblesleeve 46 and annular piston 43 will be exposed thereto. Inasmuch as thepressures inside and outside of the sleeve 46 are substantially equal,the casing-engaging members 47 and 48 will be held by springs 61 and 62in their retracted positions as shown in FIG. 2.

To set the packer 10, the weight of the tubing string 11 is graduallyslacked-off in the usual manner to move the anchor 15 and packer mandrel16 downwardly relative to the packer housing 19 which is frictionallysecured relative to the casing 13 by the drag blocks 24. It will berealized, however, that so long as the heavy spring 43 is not fullycompressed, it will support the slacked-oit weight of the tubing string11 and the anchor mandrel 25 can move downwardly with respect to thehousing 27 only as the spring 43 contracts. Nevertheless, a downwardforce equivalent to this slacked-off weight will, of course, betransmitted by the spring 43 to the packer mandrel 16. Then, once theshoulders 34 and 35 are engaged, the slacked-oit weight of the tubingstring 11 will be transmitted directly from the mandrel 25 through theseshoulders to the anchor housing 27 and packer mandrel 16. Thus, althoughan effective downward force equivalent to the amount of slacked-oifweight is continually applied to the packer mandrel 16, the anchormandrel 25 is delayed from shifting relative to the anchor housing 27until sufficient weight has been slacked-ofl to begin compressing theheavy spring 39. It will be recalled, of course, that so long as theanchor mandrel 25 has not shifted sufliciently for the reduced mandrelportion 68 to move under the O-ring 65, the two portions 66 and 67 ofthe hydraulic system will remain isolated from one another.

Accordingly, it will be appreciated that by selecting a heavy spring 39that is sufliciently strong to keep the mandrel 25 substantiallyelevated until enough weight has been slacked-ofi to displace the packerelement 20 against the casing 13, the anchor 15 will be disabled untilthe packer 10 is sealingly engaged with the casing. Then, wheneversufiicient weight has been slacked-ofi on the tubing string 11 tocompress the heavy spring 39, the anchor mandrel 25 will move downwardlyrelative to the anchor housing 27 a sufficient distance to bring thereduced mandrel portion 68 into register with the O-ring 65. Once thisoccurs, fluid communication is established between the two portions 66and 67 of the hydraulic system so as to enable the pressure within theanchor mandrel bore 31 to develop a corresponding hydraulic pressuretherein. Whenever the pressure within the mandrel bore 31 is increasedabove the hydrostatic pressure of the well annulus, the annular piston43 will be urged upwardly and develop a hydraulic pressure equal to thetubing pressure less whatever pressure is required to overcome thelighter spring 42.

It will be seen, therefore, that the anchor 15 is positively disableduntil enough weight of the tubing string 11 has been applied on thepacker mandrel 25 to sealingly engage the packing element 20 with thecasing 13. Thus, for example, should a column of cement in the tubingstring 11 develop a sufficient hydrostatic pressure within the mandrelbore 31 that would otherwise be suflicient to actuate a typicalhydraulic anchor, the casing-engaging members 47 and 46 will bemaintained in a fully retracted position until a substantial force hasbeen imparted to the packer mandrel 16. Once, however, thecasing-engaging members 47 and 48 have been urged into anchoringengagement with the adjacent casing 13, it will be appreciated that theywill be continually pressed against the casing with the force that isproportionately related to the pressure differential between theinternal mandrel bore 31 and the well annulus at any given moment.

To release the anchor 15, it is necessary only to pick up the tubingstring 11 to open the bypass valve 17 and thereby relieve any pressuredifiterential across the packing element 20. Once this pressuredifferential is relieved, the lighter spring 42 will return the pistonmember 43 to its initial position to relieve the pressure within thehydraulic system and permit the springs 61 and '62 to retract thecasing-engaging members 47 and 48. Further upward movement of the tubingstring 11 will return the anchor mandrel 25 to its original positionand,once the mandrel shoulder 38 has engaged the housing shoulder 37, thepacker mandrel 16 can be pulled upwardly to retract the slips 23 andpacking element 20.

As the tools 16, 15 and 17 are being retrieved from the well bore 12, itwill be appreciated that the hydrostatic pressure acting on the exteriorof the expansible sleeve 46 will begin decreasing as the tubing string11 is pulled further up the well bore. Since the upper portion 66 of thehydraulic system is now isolated by O-ring 65 from the lower portion 67of the hydraulic system, the hydraulic pressure in the upper portion 66of the hydraulic system will remain essentially at the hydrostaticpressure at the depth where the packer 10 was set. Thus, to prevent thisentrapped pressure from re-extending the casing-engaging members 46 and47, a relief valve, such as that shown at 76, is arranged to bleed-offany excess pressure from the upper portion 66 of the hydraulic system toits lower portion 67.

Accordingly, it will be appreciated that the present invention hasprovided a new and improved anchoring means that is capable of beingselectively disabled to permit application of a substantial force tofirst set the packer without possible restraint from the anchoringmeans. Then, when suificient force has been applied to insure the packerhas become sealingly engaged, the anchor is made operatively responsiveto an increased pressure differential from below the packer toanchoringly secure the packer mandrel against the casing with the forceproportionately related to this pressure differential.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modifications may be madewithout departing from this invention in its broader aspect; and,therefore, the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. Apparatus for packing-01f a well bore comprising: means forpacking-01f a well bore including a tubular housing member, a bodymember telescopically received in said housing member and movable withrespect thereto between an expanded position and a contracted position,and expansible packing means operatively disposed between said membersand expandable in response to movement of said body member toward saidcontracted position for packing-off the well bore; anchoring means onsaid body member and responsive to fluid pressure for anchoring saidbody member to the wall of a well bore; first means connecting said bodymember to a tubing string and responsive to a first force on the tubingstring for moving said body member toward said contracted position; andsecond means responsive to a second greater force on the tubing stringfor admitting fluid pressure in the tubing string to said anchoringmeans to secure said body member in said contracted position.

2. The apparatus of claim 1 wherein said first means includes springmeans cooperatively engaged between said body member and tubing string.

3. The apparatus of claim 1 wherein said second means includes fluidpassage means; between said anchoring means and tubing string andnormally-closed valve means responsive to movement of said body memberinto said contracted position for opening fluid communication throughsaid passage means.

4. The apparatus of claim 3 wherein said first means includes springmeans cooperatively engaged between said body member and tubing string.

5. The apparatus of claim 1 wherein said first means comprises a tubularbody telescopically arranged relative to said body member and adaptedfor connection to a tubing string, and spring means normally urging saidbody and body member apart, said spring means being yieldable inresponse to aid first force to urge said body member toward saidcontracted position.

6. The apparatus of claim 1 wherein said first means comprises a tubularbody telescopically arranged relative to said body member and adaptedfor connection to a tubing string, and spring means normally urging saidbody and body member apart, said spring means being yieldable inresponse to said first force to urge said body member toward saidcontracted position; and said second means comprises fluid passage meansbetween said anchoring means and tubing string, and normally-closedvalve means on said tubular body and responsive to movement thereof assaid body member is urged into said contracted position for openingfluid communication through said passage means.

7. The apparatus of claim 1 wherein said first means comprises a tubularbody telescopically arranged relative to said body member and adaptedfor connection to a tubing string, and spring means normally urging saidbody and body member apart, said spring means being yield able inresponse to said first force to urge said body member toward saidcontracted position; means including a floating piston member definingan enclosed piston chamber between said body and body member, and ahydraulic fluid in said chamber; and said second means comprises firstfluid passage means communicating fluid pressure within the tubingstring to said piston member for developing a hydraulic pressure in saidpiston chamber related to the tubing string pressure, second fluidpassage means between said piston chamber and anchoring means,normally-closed valve means on said tubular body and responsive tomovement thereof as said body member is urged into said contractedposition for opening fluid communication between said piston chamber andanchoring means.

8. As a sub-combination, apparatus comprising: a tubular housing memberadapted for connection to a well packer; a tubular body membertelescopically arranged with said housing member and adapted forconnection to a tubing string; anchoring means on one of said membersand including wall-engaging means extendible in response to fluidpressure; spring means normally urging said members apart and yieldablein response to a force on said body member to allow said body member tomove to a contracted position relative to said housing member; and meansfor selectively cont-rolling pressure communication between said tubingstring and anchoring means, said controlling means being operablewhenever said body member reaches said contracted position.

9. The apparatus of claim 8 further comprising means including afloating piston member defining an enclosed piston chamber between saidhousing and body members, and a hydraulic fluid in said chamber; andsaid pressurecontrolling means comprises first fluid passage meansadapted to communicate fluid pressure within said body member to saidpiston member for developing a hydraulic pressure in said piston chamberrelated to such fluid pres sure, second fluid passage means between saidpiston chamber and anchoring means, and normally-closed valve means onsaid body member and responsive to movement thereof into said contractedposition for opening fluid communication between said piston chamber andanchoring means.

10. Apparatus adapted for connection to a tubing string and comprising:means for packing-off a well bore; anchoring means connected to saidpacking-01f means and responsive to fluid pressure for securing thetubing string to the well bore; and means for selectively admittingfluid pressure to said anchoring means including telescoping membersmovable in response to movement of the tubing string between a firstposition isolating said anchoring means from fluid pressure in thetubing string and a second position where said anchoring means isresponsive to pressure in the tubing string for securing the tubingstring.

11. The apparatus of claim 10 wherein said packingofi means isselectively actuatable in response to movement of the tubing string andfurther including delay means for retarding movement of said telescopingmembers from said first position to said second position until saidpacking-01f means is actuated.

12. The apparatus of claim 10 wherein said pressureadmitting meansfurther includes piston means defining a closed hydraulic system betweensaid telescoping members, first passage means providing fluidcommunication between said piston means and tubing string, secondpassage means providing fluid communication between said hydraulicsystem and anchoring means, and means on said telescoping members foropening fluid communication through one of said passage means as saidtelescoping members move to said second position.

13. The apparatus of claim 12 wherein said packing-off means isselectively actuatable in response to movement of the tubing string andfurther including delay means for retarding movement of said telescopingmembers from said first position to said second position until saidpacking-off means is actuated.

References Cited UNITED STATES PATENTS 2,854,080 9/1958 Dale et al166-140 3,094,169 6/1963 Conrad 166-134 3,283,824 11/1966 Hoffman et al.166-212 3,306,360 2/1967 Young 166-120 3,306,361 2/1967 Lebourg 166-122ERNEST R. PURSER, Primary Examiner.

DAVID H. BROWN, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,363,695 January 16, 1968 Howard L. McGill It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

In the heading to the printed specification, lines 3 and 4 for "assignorto Schlumbeger Well Surveying Corporation" read assignor, by mesneassignments, to Schlumberger Technology Corporation column 1, line 61,after "lower" insert open Signed and sealed this 1st day of April 1969.

SEAL) nttesti dward M. Fletcher, Jr.

Ittesting Officer EDWARD J. BRENNER Commissioner of Patents

